RESUMO
1. An experiment was conducted to study the effect of naked neck gene (Na) on carcase measurements and some immunological responses of chickens. 2. The presence of naked neck gene in a single or double state increased body weight. 3. The naked neck genotypes (NaNa or Nana) exhibited higher relative weight of dressed carcase, drumstick and breast muscles compared to normally feathered individuals (nana). The proportion of abdominal fat was decreased in both naked neck genotypes compared with normally feathered ones. 4. A higher (non-specific) cell-mediated immune response was evoked in Na gene bearing birds. 5. Higher concentrations of antibodies occurred after injection of sheep red blood cells into naked neck birds, particularly at 14 d post-secondary injection. 6. The NaNa birds had a higher heterophil/lymphocyte ratio than Nana and nana siblings.